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Ab-initio electronic gaps of Ge nanodots: the role of self-energy effects

Authors: M. Marsili, S. Botti, M. Palummo, E. Degoli, O. Pulci, H-C. Weissker, M.A.L. Marques, S. Ossicini, and R. Del Sole

Ref.: J. Phys. Chem. C 117, 14229-14234 (2013)

Abstract: Nanostructuring of a material leads to enormous effects on its excited state properties. This study, through the application of different state-of-the-art ab-initio theoretical tools, investigates the effect of size on the electronic gap of nanocrystals highlighting similarities and differences with respect to equivalent silicon nanostructures. We performed both GWand DSCF calculations for the determination of their electronic structure. While it is known that DSCF corrections to the Kohn-Sham gap vanish for extended systems, the two approaches were expected to be equivalent in the limit of small clusters. However, it has been recently found that for hydrogenated Si clusters the DSCF gaps are systematically smaller than the GW ones, while the opposite is true for Ag clusters. In this work we find that the GW gaps are larger than the DSCF ones for all Ge dots, with the exception of the smallest one. Such crossing between the DSCF and the GWgap values was not expected and has never been observed before. Moreover, also for hydrogenated Si nanocrystals we found a similar behaviour. The origin of this crossing might be found in the Rydberg character of the LUMO of the smallest clusters and can also explain the qualitative differences in the comparison between GW and DSCF found in previous studies.

Citations: (Google scholar)

DOI: 10.1021/jp3121269

URL: pubs.acs.org

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Bibtex:

@article{Marsili_2013,
	doi = {10.1021/jp3121269},
	url = {https://doi.org/10.1021%2Fjp3121269},
	year = 2013,
	month = {jun},
	publisher = {American Chemical Society ({ACS})},
	volume = {117},
	number = {27},
	pages = {14229--14234},
	author = {Margherita Marsili and Silvana Botti and Maurizia Palummo and Elena Degoli and Olivia Pulci and Hans-Christian Weissker and Miguel A. L. Marques and Stefano Ossicini and Rodolfo Del Sole},
	title = {Ab Initio Electronic Gaps of Ge Nanodots: The Role of Self-Energy Effects},
	journal = {The Journal of Physical Chemistry C}
}